Chemically and electrically stabilized polymer films

ABSTRACT

A method of stabilizing a poly(paraxylylene) dielectric thin film after forming the dielectric thin film via transport polymerization is disclosed, wherein the method includes annealing the dielectric thin film under at least one of a reductive atmosphere and a vacuum at a temperature above a reversible solid phase transition temperature of the dielectric film to convert the film from a lower temperature phase to a higher temperature phase, and cooling the dielectric thin film at a sufficient rate to a temperature below the solid phase transition temperature of the dielectric thin film to trap substantial portions of the film in the higher temperature phase.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part of U.S. patent applicationSer. No. 10/116,724, filed Apr. 4, 2002 now U.S. Pat. No. 6,881,447, theentire disclosure of which is hereby incorporated by reference.

BACKGROUND

The present disclosure relates to stabilization methods for makingpolymer dielectric that is useful in the manufacturing of futureintegrated circuits (“IC's”). The present disclosure relates to, inparticular, stabilization methods for making a polymer film to achieveits best electrical performance after film deposition. In addition, itrelates to post treatment methods to retain the chemical integrity onfilm surface during and after exposure to chemical processes, especiallyafter reactive plasma etching of the dielectric that employed during thefabrication of IC's. The post treatment method will assure good adhesionand film integrity to a subsequent top layer film.

During the manufacturing of IC's, multiple layers of films aredeposited. Maintaining the compatibility and structural integrity of thedifferent layers throughout the processes involved in finishing the ICis of vital importance. In addition to dielectric and conducting layers,its “barrier layer” may include metals such as Ti, Ta, W, and Co andtheir nitrides and silicides, such as TiN, TaN, TaSi_(x)N_(y),TiSi_(x)N_(y), WN_(x), CoN_(x) and CoSiN_(x). Ta is currently the mostuseful barrier layer material for the fabrication of future IC's thatuse copper as conductor. The “cap layer or etch stop layer” normallyconsists of dielectric materials such as SiC, SiN, SiON, silicon oxide(“Si_(y)O_(x)”), fluorinated silicon oxide (“FSG”), SiCOH, and SiCH.

The schematic in FIG. 1 is used to illustrate some fundamental processesinvolved for fabrication of a single Damascene structure and futureIC's. During fabrication of future ICs, first a dielectric 110 isdeposited on wafer using a Spin-On or Chemical Vapor Deposition (“CVD”)dielectric. Then, a photoresist is spun onto the substrate and patternedusing a photo mask and UV irradiation. After removal of unexposedphotoresist and form a pattern of cured photoresist over the underlyingdielectric, a via in the dielectric layer is formed by plasma etching ofthe dielectric that is not protected by the photoresist. Then, a thinlayer (100 to 200 Å) of barrier metal 130 such as Ta is deposited usingphysical vapor deposition (“PVD”) method. This is followed by depositionof a very thin (50 to 100 Å) layer of copper seed 150 using PVD orMetal-Organic CVD (“MOCVD”). After that, the via is filled with copper140 by ECP (“Electro-Chemical Plating”) method. After the copper isdeposited, Chemical Mechanical Polishing (“CMP”) may be needed to levelthe surface of the Damascene structure. Optionally, a cap-layer isdeposited over the dielectric before coating of photoresist andphotolithographic pattering of the dielectric. The cap-layer can be usedto protect the dielectric from mechanical damage during CMP.

In our U.S. Pat. No. 6,825,303, transport polymerization (“TP”) methodsand processes for making low dielectric polymers that consist of sp²C—Xand HC-sp³C_(α)—X bonds were revealed. Wherein, X is H or preferably Ffor achieving better thermal stability and lower dielectric constant ofthe resulting polymers. HC-sp³C_(α)—X is designated for ahyper-conjugated sp³C—X bond or for a single bond of X to a carbon atomthat is bonded directly to an aromatic moiety. Due to hyper-conjugation(see p. 275, T. A. Geissman, “Principles of Organic Chemistry,” 3^(rd)edition, W. H. Freeman & Company), this C—X (X═H or F) has somedouble-double bond character, thus they are thermally stable forfabrications of future ICs.

However, we have observed that after transport polymerization, anas-deposited thin film may not achieve its best dimensional and chemicalstability. Therefore, in the U.S. Pat. No. 6,703,462, depositionconditions and post treatment methods to achieve high dimensionalstability from the as-deposited films are described.

In this application, methods to optimize the chemical stability thusachieving best electrical performance for an as-deposited film aredescribed. In addition, after reactive plasma etching of a dimensionallyand chemically stabilized film, the surface chemical composition of theresulting film has changed. Due to degradation of surface compositionunder reactive conditions, loss of adhesion between dielectric film andbarrier metal, cap layer or etch-stop layer can occur. Therefore,processing conditions are disclosed to provide good chemical stabilitythus interfacial adhesion between the dielectric film and thesubsequently deposited top layer such as the barrier metal, the caplayer or etch-stop layer.

SUMMARY

One embodiment provides a method of stabilizing a poly(paraxylylene)dielectric thin film after forming the dielectric thin film viatransport polymerization, wherein the method includes annealing thedielectric thin film under at least one of a reductive atmosphere and avacuum at a temperature above a reversible solid phase transitiontemperature of the dielectric film to convert the film from a lowertemperature phase to a higher temperature phase, and cooling thedielectric thin film at a sufficient rate to a temperature below thesolid phase transition temperature of the dielectric thin film to trapsubstantial portions of the film in the higher temperature phase.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 illustrates a single Damascene structure.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Broadly, the present disclosure pertains to processing method of polymerfilms that consist of consist of sp²C—X and HC-sp³C—X bonds (X═H or F)for fabrications of future IC's. The present disclosure also pertains toprocessing methods of polymers that consist of consist of sp²C—X andHC-sp³C^(α)—X bonds (X═H, F) and exhibit at least an irreversiblecrystal transformation temperature (“T₁”), a reversible crystaltransformation temperature (“T₂”) and a crystal melting temperature,(“T_(m)”). The present disclosure furthermore pertains to annealingmethods to stabilize an as-deposited film that prepared from TransportPolymerization. The present disclosure, in addition, pertains toannealing methods to stabilize the polymer films after a reactive plasmaetching. Furthermore, the present disclosure pertains to employment ofreductive plasma conditions for patterning polymer films that consist ofsp²C—X and HC-sp³C_(α)—X bonds (X═H, F).

I. General Chemical Aspects:

The polymer films disclosed herein are preferably prepared by theprocess of Transport Polymerization of intermediates, Ar(—CX₂-e)_(n°)under a vacuum with a low system-leakage-rate, or an inert atmosphere orboth. Where X═H or preferably F. Ar is an aromatic diradical containing6 to 30 carbons. e is a free radical having an unpaired electron. n isan integer of at least two, but less than the total available sp²C inthe aromatic moiety, Ar. Note that these low k polymers only consist ofsp²C—X and HC-sp³C_(α)—X bonds, wherein X is H or F. HC-sp³C_(α)—X isdesignated for a hyper-conjugated sp³C—X bond or for a single bond of Xto a carbon that is bonded directly to an aromatic moiety. Due tohyper-conjugation, this C—X (X═H or F) has some double-double bondcharacter, thus they are thermally stable for fabrications of futureICs.

The inert atmosphere is preferably devoid of free radical scavengers orcompounds containing active hydrogen such as H₂O and NH₃. In a specificembodiment, the intermediate has the general structure ofe-CX₂—Ar—X₂C-e. Examples of the aromatic moiety, Ar, include, but arenot limited to, the phenyl moiety, C₆H_(4−n)F_(n) (n=0 to 4), includingC₆H₄ and C₆F₄; the naphthenyl moiety, C₁₀H_(6−n)F_(n) (n=0 to 6),including C₁₀H₆ and C₁₀F₆; the di-phenyl moiety, C₁₂H_(8−n)F_(n) (n=0 to8), including C₆H₂F₂—C₆H₂F₂ and C₆F₄—C₆H₄; the anthracenyl moiety,C₁₂H_(8−n)F_(n) (n=0 to 8); the phenanthrenyl moiety, C₁₄H_(8−n)F_(n)(n=0 to 8); the pyrenyl moiety, C₁₆H_(8-n)F_(n) (n=0 to 8) and morecomplex combinations of the above moieties, including C₁₆H_(10−n)F_(n)(n=0 to 10). Isomers of various fluorine substitutions on the aromaticmoieties are also included.

In other preferred embodiments, the base vacuum is lower than 100mTorrs, and preferably below 0.01 mTorrs, to avoid moisture insidedeposition chamber. In further specific embodiments, the system leakagerate is less than about 2 mTorrs per minute, preferably less than 0.4mTorrs/minute. In another preferred embodiment, the polymer film has amelting temperature (“T_(m)”) greater than its reversible crystaltransformation temperature (“T₂”), which is greater than itsirreversible crystal transformation temperature (“T₁”), which is greaterthan its glass transition temperature (“T_(g)”). In an additionalspecific embodiment, the polymer film is a fluorinated or un-fluorinatedPPX film having a general structure of (—CX₂—C₆H₄—Z_(n)—X₂C—)_(N), whereX═H or F, Z═H or F, n is an integer between 0 and 4, and N is the numberof repeat units, greater than 10. Preferably, N is greater than 20 or 50repeat units. In another embodiment, the PPX film is transparent andsemicrystalline. In further specific embodiment, the PPX film is PPX-F,which has a repeating unit with the structure of CF₂—C₆H₄—F₂C.

Any material with low dielectric constant, such as a PPX film, has topossess several important attributes to be acceptable for integrationinto IC's.

First, the dielectric should be compositionally and dimensionallystable. The structural integrity should remain intact throughout thefabrication processes and after integration into the IC's. Theseprocesses include reactive ion etching (“RIE”) or plasma patterning,stripping of photoresist, chemical vapor or physical vapor deposition(“CVD” or “PVD”) of barrier and cap materials, electroplating andannealing of copper and chemical mechanical polishing (“CMP”) of thecopper. In addition, to maintain its electrical integrity after the ICfabrication, the dielectric should be free from contamination by barriermaterials such as Ta.

In addition, the dielectric should not cause the structural or chemicalbreakdown of a barrier or cap layer. No corrosive organic elements,particularly any that would cause interfacial corrosion, should diffuseinto the barrier or cap material. In addition, the dielectric shouldhave sufficient dimensional stability so that interfacial stressresulting from a Coefficient of Thermal Expansion (“CTE”)-mismatchbetween the dielectric and barrier or cap layer would not inducestructural failure during and after the manufacturing of the IC's.

Finally, the interfaces of the dielectric and barrier or cap layersshould be free from moisture, preventing the occurrence of ionicformation and/or migration when the IC's are operated under electricalbias.

The PPX films can be prepared by polymerization of their correspondingreactive diradical intermediates via transport polymerization. (Lee, J.,Macromol, et al., Sci-Rev. Macromol. Chem., C16(1) (1977-78)). Examplesof the PPX films and their repeat units resulting from polymerization ofthe diradical intermediates include commercially available products,such as: PPX-N (—CH₂—C₆H₄—CH₂—); PPX-F (—CF₂—C₆H₄—CF₂—); and perfluoroPPX (—CF₂—C₆F₄—CF₂—).

In general, diradical intermediates can be prepared from pyrolysis ofcorresponding dimers according to the Gorham method (U.S. Pat. No.3,342,754). They can also be prepared by pyrolysis of monomers andco-monomers (see U.S. patent application “Integration of Low ε Thin Filmand Ta Into Cu Dual Damascene,” Ser. No. 09/795,217, the entire contentof which is hereby incorporated by reference) under vacuum conditions oran inert atmosphere. The vacuum should be lower than about 100 mTorrs,preferably about 30 mTorrs. The vacuum system should also have an air orsystem leakage rate of less than about 2 mTorrs/minute, preferably lowerthan 0.4 mTorrs/minute. An inert atmosphere is an atmosphere that isdevoid of free radical scavengers such as water and oxygen, or devoid ofa compound containing “active hydrogen,” such as an —OH, —SH, or —RNHgroup.

The resultant PPX products can be transparent or opaque films or inpowder form depending on processing conditions. Only continuous filmscan be useful for IC manufacturing applications. Opaque films thatcontain micro-cracks or spherulites with crystal sizes even insub-micrometer range are not useful in integrated circuits. Transparentfilms can be in an amorphous or semicrystalline PPX phase. When itscrystalline phase is less than 10 nm or lower, semicrystalline PPX filmscan be useful for the manufacturing of future IC's. Amorphous PPX filmsconsist of random polymer chain orientations, which will create equalinterfacial stress in all directions, thus avoiding problems that areassociated with semi-crystalline polymers. However, amorphous PPX filmsthat consist of a regular chemical structure or repeating unit in theirbackbone structures can be re-crystallized into semicrystalline films.For example, these amorphous PPX films can transform intosemicrystalline films when they are exposed to temperatures 20 to 30° C.above their glass transition temperature, T_(g). Sincere-crystallization will induce dimensional change and PPX-N and PPX-Fhave T_(g)'s of only about 65 and 172° C. respectively, the amorphous orlow crystalline PPX-N and PPX-F are not useful for the manufacturing offuture IC's.

Transparent semicrystalline PPX-N films have been obtained bycontrolling primarily the substrate temperature and chemical feed rateunder a particular range of vacuum pressure in a deposition chamber.Detailed conditions and general mechanisms for making transparentsemicrystalline PPX-N films have been described previously (Wunderlichet al., J. Polym. Sci. Polym. Phys. Ed., Vol. 11 (1973) and Wunderlichet al., J. Polym. Sci. Polym. Phys. Ed., Vol. 13 (1975)). The suitablevacuum range is about 1 to about 100 mTorrs, preferably about 5 to about25 mTorrs. Under this vacuum range, the crystal form and crystallinityare result directly from the feed rate and substrate temperature.Suitable substrate temperatures can range from about −10 to about −80°C., preferably from about −25 to about −45° C. During IC fabrication,wafer temperature is controlled by the cooling of an electric chuck or awafer holder using a coolant. A wafer temperature below about −45° C. isdesirable for obtaining a high deposition rate, but it requires aspecial, expensive coolant such as fluorocarbon fluid or silicone oil.

It should be noted that at very low substrate temperatures, about −50 to−60° C., nucleation rates can be very high and hetero-epitaxial orhighly oriented crystal growth is possible. The resulting polymercrystals would therefore be in “transcrystalline” or “columnar” forms.At these low temperature ranges, diradicals are absorbed very rapidlyand the film growth rates are very high. However, this is achieved atthe expense of the resulting crystallinity due to the entrapment of lowmolecular weight PPX-F units or other defects. A PPX-F film with lowcrystallinity can have poor dimensional stability at temperatures aboveits T_(g), about 172° C. PPX-F films prepared under these conditionsstill need to be properly annealed before they can be useful for themanufacturing of future IC's. Thin films consisting of even more thanfew percent of low molecular weight PPX-F polymers are not useful due tothe poor dimensional and chemical stability during the manufacturing ofIC's.

Therefore, under the vacuum range of a few mTorrs and at substratetemperatures ranging from about −25 to about −45° C., desirable thinfilms with high crystallinity can be obtained by adjusting the feed rateof the precursors. Depending on the chemistries and precursors employedfor the preparation, the feed rates can be very different. For example,at a feed rate from 1 to 10 standard cubic centimeters per minutes(“sccm”) of the monomer Br—CF₂—C₆H₄—CF₂—Br and at a substratetemperature from about −30 to about −50° C., crystalline PPX-F films canbe obtained. When the substrate temperature is higher than about 10° to20° C., nucleation is difficult due to the low adsorption of diradicalintermediates. However, under very high feed or flow 3 rates, polymercrystal growth can still be possible after an induction period toovercome primary nucleation on the substrate. PPX-F films prepared underthese conditions can have high crystallinity. Even without annealing,these PPX-F films can be useful for integration into future IC's.Furthermore, it is possible to prepare a high temperature crystal formof PPX-F at substrate temperatures above 40-60° C., though thedeposition rate will suffer enormously.

One should note that the above deposition processes inherently resultedin an as-deposited film with both chemical and dimensional instabilitiesthat need further explanations as described in the following paragraphs.

Chemical Instability of as-deposited Films: In general, the dielectricfilms disclosed herein are formed in vacuum by step polymerization ofmany intermediate molecules or intermediates called diradicals. Eachdiradical carries an unpaired electron on both ends of the intermediate.We call the diradical as an intermediate, because it is very reactivetoward another diradical. It has a lifetime in 10⁻⁶ second or less, whencolliding at solid state with another diradical, even at temperatures aslow as −100° C. We name reaction for polymer-chain extension as steppolymerization because the polymerization reaction occurring one step atime.

Note that each diradical can grow from both ends of the intermediate,and after each step of the reaction, because the added polymer alwaysleaves another unpaired electron at the polymer chain end. Thus, aspolymer chain grows, each polymer-chain always bears two unpairedelectrons at both ends of the polymer. This polymer chain is alive andcan grow further as long as there is no scavenger is around orphysically the chain-end is buried under other polymer chains that growover the end. A compound that consists of X—H group or oxygen, herein Xis nitrogen, Sulfur and oxygen, is very effective toward the unpairedelectron, thus we call then scavengers, and it will stop the chaingrowth.

Since scavenger is absence under vacuum, the resulting The dielectricfilm can consist of living polymers or polymer with unpaired electron atpolymer chain ends, because their chain ends are buried inside the filmsand still reactive toward scavengers. Note that most scavengers havesmaller molecular size and can still diffuse to these chain ends. Theresulting products that carrying —C═O or C—X (X—O, N, S) bonds,unfortunately, are very thermally unstable at high temperatures. Thesechemical groups decompose at temperatures from 250 to 400° C. in fewminutes. In addition, presence of these unpaired electrons at polymerchain ends can result in poor electrical properties.

The above problems will pose a challenge to make chemically andelectrically stable dielectric film, if the as-deposited film is exposedto air before these living chain ends are converted to some stablechemical groups. One solution for this problem is to anneal anas-deposited dielectric film with hydrogen under high temperature beforethe film is removed from deposition chamber or vacuum system. Thisannealing process can achieve both high crystallinity for betterdimensional stability and chemical stability by capping all unpairedchain ends with C—H bond, which is more stable than C—C or C—O bonds.

Dimensional Instability of as-deposited Films: One of the importantrequirements for the dielectric film is to achieve good adhesion to thebarrier layer, etch stop layer and the cap layer. Scientificallyspeaking, adhesion strength can be examined by looking into its chemicaland physical contributors

Good physical or mechanical adhesion calls for good mechanicalinterlocks with larger contacting surfaces. In addition, to achieve goodmechanical interlocking, the dimensional stability of the interlockingfaces has to be stable in view of their relative dimensional expansionunder temperature incursion. Since all inorganic layers used in ICfabrications have lower Coefficient of Thermal Expansion (“CTE”) thanpolymer dielectric, it is thus desirable to lower the CTE of the polymerdielectric by either increase their cross-linking density or increasetheir crystallinity.

Dimensional stability of an as-deposited film may be achieved 1) bycontrolling the deposition conditions, such as feed rate and substratetemperature to obtain a thermally more stable crystal form, and 2) bypost-annealing treatment of an as-deposited film to increase itscrystallinity. The details for both the processing conditions and thepost annealing methods are described in the following paragraphs.

II. Methods for Making Dimensionally Stable Films:

Without proper processing conditions, high crystalline PPX filmsobtained through re-crystallization will fail when subjected tofabrication processes currently employed for making IC's. In the IC'sthat use electrically plated copper as a conductor, the requiredannealing temperature for the copper ranges from 300° C. for one hour to350° C. for 30 minutes. Some integration processes also require asubstrate temperature of 400° C. In addition, during packagingoperations of the IC's, such as wire bonding or solder reflow,structural stability of the dielectric at temperatures as high as 300 to350° C. is also required. Therefore, any useful PPX film needs to bechemical and dimensionally stable at temperatures up to 300 to 350° C.,preferably 350 to 400° C. for at least 30 minutes.

DSC measurements, performed at a 10 to 15° C. per minute heating rateand under a nitrogen atmosphere, show a peak T_(g) for PPX-F around 170°C. and an Alpha to Beta-1 irreversible crystal transformationtemperature, (“ICT”), ranging from 200° to 290° C. with a peaktemperature, T₁, around 280° C. In addition, there are also a Beta-1 toBeta-2 reversible crystal transformation temperature (“RCT”), rangingfrom 350 to 400° C. with a peak T₂ around 396° C. and a meltingtemperature, T_(m), ranging from 495 to 512° C. with a peak T_(m) around500° C. For comparison, the corresponding T_(g), T₁, T₂, and T_(m) forPPX-N are respectively, 65°, 230°, 292° and 430° C. (Wunderlich et al.,J. Polym. Sci. Polym. Phys. Ed., Vol. 11 (1973) and Wunderlich et al.,J. Polym. Sci. Polym. Phys. Ed., Vol. 13 (1975)). The Alpha to Beta-1crystal transformation occurring at T₁ is irreversible, while the Beta-1to Beta-2 crystal transformation, at T₂, is reversible for both PPX-Nand PPX-F. When a crystalline PPX-N or PPX-F film is exposed totemperatures approaching its T₁, polymer chains in its Alpha crystallinephase will start to reorganize and transform into a more thermallystable Beta-1 crystal phase. Once this happens, the film will never showits Alpha phase again, even by cooling the film below its T₁. However,if a PPX-N or PPX-F film is cooled slowly from at or above its T₂ to atemperature below its T₂, the less dimensionally stable Beta-1 crystalphase will reform.

One way to maximize the dimensional stability of the PPX-N or PPX-F filmis to trap the polymer chains in their most thermally stable form, theBeta-2 crystal phase, if the film is to be used or exposed totemperatures approaching T₂. Then, if the film is exposed totemperatures approaching or surpassing its T₂, crystal transformationcannot occur, because the film is already in its Beta-2 form.Eliminating this phase transformation ensures the dimensional stabilityof the film. In principle, when the film is in its Beta-2 crystal phase,its dimensional stability is still assured even at temperaturesapproaching 50 to 60° C. below its T_(m). A highly crystalline (greaterthan 50% crystallinity) PPX-F film in a Beta-2 crystal phase can bedimensionally stable up to 450° C. for at least 30 minutes, limited onlyby its chemical stability.

A polymer film that exhibit a reversible crystal transformationtemperature, T₂, and a crystal melting temperature, T_(m) can beobtained by optimizing the feed rate and substrate temperature duringfilm deposition. By controlling the feed rate and substratetemperatures, semicrystalline films consisting of either Alpha or Betaphase crystals have been prepared (Wunderlich et al., J. Polym. Sci.Polym. Phys. Ed., Vol. 11 (1973) and Wunderlich et al., J. Polym. Sci.Polym. Phys. Ed., Vol. 13 (1975)). When the substrate temperature islower than the melting temperature of its intermediate diradical, Tdm,and when the feed rate is low (less than 0.07 g/minute), thepolymerization of crystalline diradicals can result in PPX-N films thatare predominantly in the Beta crystal phase and have high crystallinity.Conversely, when the substrate temperature is higher than the Tdm,polymerization of liquid diradicals and subsequent crystallization ofpolymers often results in PPX-N films that are in the Alpha crystalphase and have low crystallinity.

The above film on wafer is generally referred as an “as-deposited film.”Before it is removed from the deposition system and when it is stillunder the vacuum condition, the as-deposited film may need to be furtherstabilized in order to achieve sufficient chemical and dimensionalstability for use in integrated circuits.

Accordingly, a stabilized film can be obtained by annealing theas-deposited film to a temperature approaching to or above its T₂ andunder the presence of hydrogen and then quickly quenching the films toat least 30 to 60° C. below their T₂. For instance, a PPX-F film that ispredominantly in the Beta-2 crystal phase can be obtained by heating thefilm to 450° C. for 5 minutes, then quenching the film to 330° C. at acooling rate of approximately 1° C./second or faster. When the postannealing was performed under 3 to 20% hydrogen conditions, theresulting films also exhibited very low leakage current comparing to theas-deposited film and an annealed film that was obtained under vacuumconditions. Other cooling rates may also be suitable, including but notlimited to rates between approximately 1° C./second and 15° C./second,or even faster. Alternatively, slower cooling rates may also be used forsome films. For example, it has been determined that a significantamount of beta-2 phase in can be preserved in PPX-F by using a coolingrate of approximately 50° C./minute.

Actual polymer chain motions for solid state transition or phasetransformation can start from 30 to 60° C. below the correspondingT_(g), T₁, T₂ and T_(m) depending on the history of the films, degree ofcrystallinity, perfection of crystals, or the existence of various lowmolecular weight material in the crystalline phase (Wunderlich,Macromolecular Physics, Vol. 1-2 (1976). In fact, the Beta-1 to Beta-2transition can start at temperatures ranging from 40 to 50° C. below T₂,(about 396° C.) for PPX-F films. Therefore, by exposing a depositedPPX-F film to 350° C. for one hour, the quenched PPX-F film alsoexhibited a high content of Beta-2 phase crystallinity. The presence ofBeta-2 crystals can be verified by DSC. When a PPX-F film containing ahigh percentage of Beta-2 phase crystals was scanned by DSC from 25 to510° C. under a nitrogen atmosphere, only T_(m) was observed and not T₁or T₂.

The maximum temperature, T_(max), which is encountered during themanufacturing of IC's, will undoubtedly be lowered over time due totechnological advancements. Improvements in copper plating chemistriesand the perfection of the resulting copper films will lower the requiredannealing temperatures. In addition, physical vapor depositiontemperatures for barrier layers or cap layers could be reduced totemperatures below 400° C. Once this occurs, the maximum processingtemperature, T_(max), can be lowered to temperatures below 350° C.,possibly as low as 325° to 300° C. In that case, the annealing of PPX-Ffilms can be performed at temperatures 30 to 50° C. below T₂ (396° C.for PPX-F) or as low as temperatures 10 to 20° C. above T₁ (280° C. forPPX-F). However, the annealing should be done at a temperature equal toor higher than the T_(max) for 1 to 60 minutes and preferably for 3 to 5minutes.

Note that all the above post annealing should be conducted before anas-deposited film is removed from the deposition systems and isconducted in the presence of hydrogen. Preferably, the reductiveannealing is conducted not inside the deposition chamber but inside apost treatment chamber. The reductive annealing is conducted under anatmosphere consisting of 0.1 to 100, preferably 3 to 6% of H in argonand at high temperatures conditions described in the above.

III. Methods for Stabilizing Films after Plasma Etching:

During fabrication of future IC's, a stabilized film obtained from theabove will subject to further process as follows: First, a photoresistis spun onto a substrate and patterned using a photo mask and UVirradiation. After removal of unexposed photoresist, a via pattern ofphotoresist over the underlying dielectric, a via in the dielectriclayer is formed by plasma etching of the dielectric that is notprotected by the photoresist. A thin layer (100 to 200 Å) of barriermetal such as Ta is then deposited using a physical vapor deposition(“PVD”) method. Optionally, a cap-layer is deposited over the dielectricbefore coating of photoresist and photolithographic pattering of thedielectric. The cap-layer is used to protect the dielectric frommechnical damage during CMP.

The low k films that consist primarily of C, H and F and single bonds ofsp²C—F and HC-sp³C—F types can utilize oxidative plasma to achieve highetching rate vs. that of photoresist. Under treatment under 0.02 W/cm²to 2.0 W/cm², preferably 0.04 W/cm² to 1.0 W/cm² of discharge power andunder 20 to 2000, preferably 50 to 500 mTorrs of oxygen pressure, anetching rate ranging from 500 to 5000 Å/minute can be obtained. However,after more than few Angstroms of polymers were removed from the filmsurface, the composition of the resulting surface became highlyoxidized. The freshly etched polymer surfaces are NOT suitable forfabrication of IC's, because they consist of thermally unstableoxygenated carbon groups, such as —CX—O, —XC═O, —CX—O—O—X and—(C═O)—OXbonds (X═H or F). These oxygenated carbon bonds will decompose attemperatures above 200 to 350° C. In addition, these types of oxidizedsurfaces tend to adsorb moisture and form hydrogen bonded water on theirsurfaces. Thus, if a barrier metal, cap layer or etch stop layer isdeposited over the oxidative plasma treated surface, loss of adhesioncan easily happen after the coating process or during subsequentprocesses.

In addition, patterning of the dielectric films disclosed herein hasalso been performed by dry etching using nitrogen plasma. For instance,nitrogen plasma patterning can be done using 30 W of plasma power under900 mTorrs of pressure. The resultant film surfaces were foundunsuitable for obtaining good adhesion. We suspect that some nitrogenwere chemically reacted with the C—X (X═H or F) of the dielectricsurfaces and converted to unstable —C—N or polar —C═N— bonds both aredesirable for IC fabrication applications.

A method to re-stabilize the reactive plasma etched treated polymersurfaces that is obtained from the oxygen or nitrogen plasma etching,for further coating includes reductive annealing the surfaces underhydrogen atmosphere at high temperatures. Alternatively, by treating theoxidized surfaces first using non-reactive plasma then followed with areductive annealing at high temperatures. The non-reactive plasma forinstance can be conducted under the presence of argon gas. Thenon-reactive plasma is believed, in addition to remove some of theoxygenated or nitrogen-reacted carbon groups on surfaces, also toroughen these surfaces for better mechanical adhesion during thesubsequent coating. The reductive annealing under high temperature isprimarily used to reduce the sp²C—Y and HC-sp³C—Y (Y═O or N) groups backto sp²C—X and HC-sp³C_(α)—X. Herein, X is F, or preferably H. Note thatthe above methods will result in thermally stable sp²C—X andHC-sp³C_(α)—X bonds (X═H or F) that are thermally stable forfabrications of future IC's.

Note that the above re-stabilization methods are not useful if theoriginal low k films consist of other unstable chemical bonds, such assp³C—X bonds (X═H or F). These polymers consist of regular tetrahedronsp³C—X bonds, such as —CX³ and —CX₂— bonds (X═H or F) that its carbon isnot an Alpha carbon to an aromatic moiety. These sp³C—X bonds-containingpolymers are not stable enough for fabrications of future IC's thatrequire a minimum thermal stability at temperatures of 350° C. or higherfor 30 minutes or longer. Therefore, even theirafter-oxidative-plasma-etched surfaces are treated with the methodsdescribed herein, the thermal stability of their resulting polymers willNOT be improved beyond the thermal stability of the original polymers,thus will still not useful for fabrication of future IC's.

The reductive annealing can be conducted under an atmosphere of 1 to30%, preferably 3 to 10% of hydrogen in argon or other noble gases andat 410 to 450° C. for 2 to 60, preferably from 3 to 10 minutes. Thenon-reactive plasma treatment can be conducted under treatment under0.01 W/cm² to 1.0 W/cm², preferably 0.04 W/cm² to 0.4 W/cm² of dischargepower and under 20 to 2000, preferably 50 to 500 mTorrs of argonpressure.

Alternatively, the dry etching by plasma partnering of a polymer filmcan be conducted in the presence of an reductive gas composition, forinstance, from 20 to 2000, preferably 100 to 1000 mTorrs of 3 to 10% ofhydrogen in argon or other noble gases and under 0.01 W/cm² to 1.0W/cm², preferably 0.04 W/cm² to 0.4 W/cm² of discharge power.

IV. Experiments and Results:

The following are offered by way of example, and are not intended tolimit the scope of the invention in any manner.

Experiment 1: Deposition of PPX-F was performed using a system thatconsisted of a quartz reactor with porous SiC inserts that were heatedto a temperature of about 580° C. by an infrared heater. The precursoris YCX₂—C₆H_(4−n)Z_(n)—X₂CY, where X═F, n=0 and Y=—Br. It was heated ina sample holder at 65° C. to achieve a feed rate of at least 0.1mMol/minute and transported to the reactor under a system vacuum ofabout 20 mTorrs. The reacted precursors or diradical intermediates weretransported to a 200-mm wafer that was kept at −35° C. using anelectrical static chuck (“ESC”). The film thickness is about 3483 Å (LowW^(c) B₂).

Experiment 1A: The resulting film from the Experiment 1 was analyzedusing X-ray diffraction (“XRD”). The film has a diffraction angle, 2θ at19.2 degree with relative peak intensity of 520, indicative of Beta 2crystals in the film that has low crystallinity (“W^(c)”). After thefilm was annealed on hot plate at 350° C. for 10 minutes, only peakintensity changes to about 800. After the film was annealed on hot plateat 390° C. for 10 minutes, its peak intensity changes to about 870.After the film was annealed on hot plate at 405° C. for 10 minutes, itspeak intensity changes to about 1000. After the film was annealed on hotplate at 405° C. for 60 minutes and slowly cooled to 25° C., itsdiffraction angle, 2θ shifted to 20.3 degree with a relative peakintensity of 6000, indicative of Beta 1 crystals in the film that hasvery high crystallinity.

Experiment 1B: The film obtained from the Experiment 1 was annealed onhot plate at 410° C. for 30 minutes and slowly cooled to 25° C., itsdiffraction angle, 2θ shifted to 20.3 degree with a relative peakintensity of 6000, indicative of Beta 1 crystals in the film that hashigh crystallinity.

Experiment 1C: The film obtained from Experiment 1 was annealed on hotplate at 405° C. for 60 minutes and slowly cooled to 25° C., the XRDshowed it consisted of Beta 1 crystal with high crystallinity. The filmon silicon wafer was coated with a 200 Å of Ta using PVD process. Thesample was annealed at 350° C. for 30 minutes. The resulting sampleshowed no breakage of Ta. Rutherford Backscattering Spectroscopy (“RBS”)analysis of the profile showed Ta did not diffused into polymer, and theorganic elements did not diffused inside the Ta.

Experiment 1D: The film obtained from the Experiment 1 was annealed onhot plate at 300° C. for 30 minutes, only peak intensity changes toabout 500 (B₂). After the film was annealed on hot plate at 450° C. for30 minutes and quickly quenched to room temperature, the film stillshowed a diffraction angle, 2θ at 19.2 degree with a peak intensitychanges to about 3000, indicative of Beta 2 crystal in the film withhigh crystallinity. The film on silicon wafer was coated with a 200 Å ofTa using PVD process. The sample was annealed at 350° C. for 30 minutes.The resulting sample showed no breakage of Ta. Rutherford BackscatteringSpectroscopy (“RBS”) analysis of the profile showed no Ta diffused intopolymer, nor organic elements diffused inside the Ta.

In summary, the above experiments indicated that high crystalline Beta 1and Beta 2 are stable, when Ta is used as barrier layer and theannealing condition is no more than 350° C. for 30 minutes. However, ifa prolong annealing time or a higher temperature is required, it ispreferred to use a PPX-F film that consisted of highly crystalline Beta2 crystal phase, because it is more dimensionally stable than the Beta 1crystals.

Experiment 2: The film obtained from Experiment 1 (Low W^(c) B₂) washeated to 350° C. at a 15° C./minute heating rate, held isothermally atabout 350° C. for 30 minutes under 10⁻⁷ vacuum, then quenched at 60°C./minute to room temperature. The resulting film is about 3472 Å (MedW^(c) B₂).

Experiment 3: The film obtained from Experiment 1 (Low W^(c) B₂) washeated to 410° C. at a 15° C./minute heating rate, held isothermally atabout 410° C. for 30 minutes under 10⁻⁷ vacuum, then quenched at 60°C./minute to room temperature. The resulting film is about 3395 Å (HiW^(c) B₂).

Experiment 4: The film obtained from Experiment 1 (Low W^(c) B₂) washeated to 400° C. at a 15° C./minute heating rate, held isothermally atabout 400° C. for 60 minutes nitrogen atmosphere, then slowly cooled toroom temperature (Hi W^(c) B₁).

Experiment 5: The film obtained from Experiment 1 (Low W^(c) B₂) wascoated with a 250 Å of Ta using PVD process. Peel test using a 3MScotch® tape showed adhesion failure at Si wafer interface. After thesample was annealed at 350° C. for 30 minutes under 10⁻⁷ vacuum, thesample Ta was heavily corroded and cracked with dielectric film.

Experiment 6: The film obtained from Experiment 2 (Med W^(c) B₂) wascoated with a 250 Å of Ta using PVD process. Peel test using a 3MScotch® tape showed no adhesion failure. However, after the sample wasannealed at 350° C. for 30 under 10⁻⁷ vacuum, the sample failed atdielectric and Si-wafer interface when subjected to peeling test using3M scotch tape. In addition, Ta showed slightly cracking.

Experiment 7: The film obtained from Experiment 3 (Hi W^(c) B₂) wascoated with a 250 Å of Ta using PVD process. Peel test using a 3MScotch® tape showed no adhesion failure. However, after the sample wasannealed at 350° C. for 30 under 10⁻⁷ vacuum, the sample failed atdielectric and Si-wafer interface when subjected to peeling test using3M scotch tape. In addition, Ta showed slightly cracking.

Experiment 8a: The film obtained from Experiment 4 (Hi W^(c) B₁) wascoated with a 250 Å of Ta using PVD process. Peel test using a 3MScotch® tape showed no adhesion failure. After the sample was annealedat 350° C. for 30 minutes under 10⁻⁷ vacuum, Ta showed slightly sign ofcorrosions. When subjected to peeling test using a 3M scotch tape, thesample showed no adhesion failure.

Experiment 8b: The film obtained from Experiment 4 (Hi-W^(c) B₁) wasfurther heated to 410° C. at a 15° C./minute heating rate, heldisothermally at about 410° C. for 30 minutes under 10⁻⁷ vacuum, thenquenched at 60° C./minute to room temperature (Maxi-W^(c)B₂). The samplewas coated with a 250 Å of Ta using PVD process. Peel test using a 3MScotch® tape showed no adhesion failure. After the sample was annealedat 350° C. for 30 minutes under 10⁻⁷ vacuum, Ta showed no sign ofcorrosions. When subjected to peeling test using a 3M Scotch® tape, thesample showed no adhesion failure.

Experiment 9: The film obtained from Experiment 4 (Hi-W^(c) B₁) wasetched at 50 Watts of power and under 50 mTorrs of oxygen plasma toremove 400 Å of polymer films. The film was then coated with a 250 Å ofTa using PVD process. The samples passed a peeling test using a 3MScotch® tape. After the sample was annealed at 350° C. for 30 minutesunder 10⁻⁷ vacuum, the Ta only showed spotty corrosions at the edge oftest specimens. When subjected to peeling test using a 3M Scotch® tape,the sample peeled off 50% at low k and Ta interface.

Experiment 10: The film obtained from Experiment 4 (Hi-W^(c) B₁) wasetched at 50 Watts of power and under 50 mTorrs of oxygen plasma toremove 400 Å of polymer films. The film was annealed under 10⁻⁷ Torrs ofvacuum and at 410° C. for 30 minutes and then quenched to roomtemperature (Maxi W^(c) B₂). The film was then coated with a 250 Å of Tausing PVD process. The samples passed a peeling test using a 3M scotchtape. After the sample was annealed at 350° C. for 30 minutes under 10⁻⁷vacuum, Ta only showed spotty corrosions at the edge of test specimens.When subjected to peeling test using a 3M Scotch® tape, the samplepeeled 10% at low k and Ta interface.

Experiment 11: The film obtained from Experiment 4 (Hi W^(c) B₁) wasannealed under 10⁻⁷ Torrs of vacuum and at 410° C. for 30 minutes andthen quenched to room temperature (Maxi W^(c) B₂). Then it was etched at50 Watts of power and under 50 mTorrs of oxygen plasma to remove 400 Åof polymer films. The film was then coated with a 250 Å of Ta using PVDprocess. The samples passed a peeling test using a 3M Scotch® tape.After the sample was annealed at 350° C. for 30 minutes under 10⁻⁷vacuum, Ta only showed spotty corrosions at the edge of test specimens.When subjected to peeling test using a 3M Scotch®tape, the sample failedadhesion at low k and Ta interface.

Experiment 12: The film obtained from Experiment 4 (Hi W^(c) B₁) wasannealed under 10⁻⁷ Torrs of vacuum and at 410° C. for 30 minutes andthen quenched to room temperature (Maxi W^(c) B₂). Then it was etched at50 Watts of power and under 50 mTorrs of oxygen plasma to remove 400 Åof polymer films. The film was annealed under 10⁻⁷ Torrs of vacuum andat 410° C. for 30 minutes and quenched to 25° C. (Maxi W^(c) B₂). Thefilm was then coated with a 250 Å of Ta using PVD process. The samplespassed a peeling test using a 3M Scotch® tape. After the sample wasannealed at 350° C. for 30 minutes under 10⁻⁷ vacuum, Ta only showedspotty corrosions at the edge of test specimens. When subjected topeeling test using a 3M Scotch® tape, the sample failed adhesion at lowk and Ta interface.

Experiment 13: The film obtained from Experiment 4 (Hi W^(c) B₁) wasannealed under 10⁻⁷ Torrs of vacuum and at 410° C. for 30 minutes andthen quenched to room temperature (Maxi W^(c) B₂). Then it was etched at50 Watts of power and under 50 mTorrs of oxygen plasma to remove 400 Åof polymer films. The film was annealed then under 3% H₂ in argon at410° C. for 30 minutes (Maxi W^(c) B₂). The film was then coated with a250 Å of Ta using PVD process. The sample was then annealed at 350° C.for 30 minutes under 10⁻⁷ vacuum. The sample failed adhesion at low kand Si-wafer interface when subjected to peeling test using a 3M Scotch®tape.

Experiment 14: The film obtained from Experiment 4 (Hi W^(c) B₁) wasannealed under 10⁻⁷ Torrs of vacuum and at 410° C. for 30 minutes andthen quenched to room temperature (Maxi W^(c) B₂). Then it was etched at50 Watts of power and under 50 mTorrs of oxygen plasma to remove 400 Åof polymer films. The film then was treated at 30-Watts power with 900mTorrs of N₂ plasma. The film was then coated with a 250 Å of Ta usingPVD process. The sample was then annealed at 350° C. for 30 minutesunder 10⁻⁷ vacuum. The sample failed adhesion at low k and Ta interfacewhen subjected to peeling test using a 3M Scotch® tape.

Experiment 15: The film obtained from Experiment 4 (Hi W^(c) B₁) wasannealed under 10⁻⁷ Torrs of vacuum and at 410° C. for 30 minutes andthen quenched to room temperature (Maxi W^(c) B₂). Then it was etched at50 Watts of power and under 50 mTorrs of oxygen plasma to remove 400 Åof polymer films. The film then was treated at 30 Watts of dischargepower and 900 mTorrs of N₂ plasma. Then, the film was annealed under 3%H₂ in argon at 410° C. for 30 minutes and then quenched to roomtemperature (Maxi W^(c) B₂). The film was then coated with a 250 Å of Tausing PVD process. The sample was then annealed at 350° C. for 30minutes under 10⁻⁷ vacuum. The sample failed adhesion at low k andSi-wafer interface when subjected to peeling test using a 3M Scotch®tape.

Experiment 16: The film obtained from Experiment 4 (Hi W^(c) B₁) wasetched at 50 Watts of discharge power and under 50 mTorrs of oxygenplasma to remove 400 Å of polymer films. The film then was treated at 30Watts of discharge power and 900 mTorrs of N₂ plasma. The film was thencoated with a 250 Å of Ta using PVD process. The sample was thenannealed at 350° C. for 30 minutes under 10⁻⁷ vacuum. The samplepartially peeled at low k and Ta interface when subjected to peelingtest using a 3M Scotch® tape.

Experiment 17: The film obtained from Experiment 4 (Hi W^(c) B₁) wasetched at 50 Watts of power and under 50 mTorrs of oxygen plasma toremove 400 Å of polymer films. The film was annealed under 3% H₂ inargon at 410° C. for 30 minutes and then quenched to room temperature(Maxi W^(c) B₂). The film was then coated with a 250 Å of Ta using PVDprocess. The sample was then annealed at 350° C. for 30 minutes under10⁻⁷ vacuum. The sample was partially peeled at low k and Ta interfacewhen subjected to peeling test using a 3M Scotch® tape.

Experiment 18: The film obtained from Experiment 4 (Hi W^(c) B₁) wasetched at 50 Watts of power and under 50 mTorrs of oxygen plasma toremove 400 Å of polymer films. The film then was treated at 30 Watts ofdischarge power and 900 mTorrs of N₂ plasma. The film was then annealedunder 3% H₂ in argon at 410° C. for 30 minutes. The film was then coatedwith a 250 Å of Ta using PVD process. The sample was then annealed at350° C. for 30 minutes under 10⁻⁷ vacuum. The sample showed NO peelingwhen subjected to peeling test using a 3M Scotch® tape.

The results obtained from the above Experiments 2 to 18 are summarizedin the followings:

1. A higher temperature (>/=) 410° C. annealing to maximizecrystallinity would prevent film structure change and adhesion failureduring 350° C. annealing (Expts. 8b).

2. Due to decomposition of oxygenated chemical bonds at interfaces, alloxidized surfaces failed to retain good adhesion between Ta todielectric during a subsequent annealing at high temperature (>/=350°C./0.5 hr) (Expts. 9 to 12).

3. Non-oxidative plasma increased surface roughness and increasedadhesion of Ta to dielectric.

4. N₂ plasma roughened the dielectric surfaces, but also caused thechanges of C—X (X═F) bonds to C—Y (Y═N) bonds, thus did not provide goodadhesion between Ta and dielectric when exposed to high temperatures.

5. Reductive annealing at high temperatures for oxidized dielectricsurfaces reduced oxidized carbon bonds back to sp²C—X and HC-sp³C_(α)—Xbonds (X═H or F) and thermally stabilized the dielectric surfaces forfurther coatings.

6. Best adhesion can be obtained by combining a roughening of filmsurfaces using argon or argon/H plasma and reductive annealing of theoxidized at high temperature (Expt. 18), or an reductive annealingalone.

7. High crystalline B₂ crystal form of PPX-F seemed to degrade at Si anddielectric interfaces during reactive plasma etching of PPX-F more thanhigh crystalline B₁ (Expts. 15 vs. 18).

While the present invention has been particularly described, inconjunction with a specific preferred embodiment, it is evident thatmany alternatives, modifications and variations will be apparent tothose skilled in the art in light of the foregoing description. It istherefore contemplated that the appended claims will embrace any suchalternatives, modifications, and variations as falling within the truescope and spirit of the present invention.

REFERENCES CITED

The following U.S. Patent Documents and publications are incorporated byreference herein.

U.S. Patent Documents

U.S. Pat. No. 3,342,754 issued in September of 1967 with Gorham listedas an inventor.

U.S. Pat. No. 6,302,874 issued in October of 2001 with Zhang et al.listed as an inventor.

U.S. Pat. No. 6,703,462 issued in March 2004 with Lee listed as aninventor.

U.S. Pat. No. 6,797,343 issued in September 2004 with Lee listed asinventor.

U.S. Pat. No. 6,825,303 issued in November of 2004 with Lee listed as aninventor.

U.S. patent application Ser. No. 10/029,373, filed Dec. 17, 2001.

OTHER REFERENCES

Brun A. E. 100 nm: The Undiscovered Country, SemiconductorInternational, p79, February 2000.

Chung Lee, “Transport Polymerization of Gaseous Intermediates andPolymer Crystals Growth” J. Macromol. Sci-Rev. Macromol. Chem., C16 (1),79-127 (1977-78), pp79-127).

Geissman T. A. Principles of Organic Chemistry, 3rd edition, W. H.Freeman & Company, p275.

Kudo et al., Proc. 3d Int. DUMIC Conference, 85-92 1997.

LaBelle et al., Proc, 3d Int. DUMIC Conference, 98-105 1997.

Lee, J., et al. Macromol Sci-Rev. Macromol. Chem., C16(1) 1977-78.

Lu et al, J. Mater. Res. Vol, 14(1), p246-250, 1999; Plano et al, MRSSymp. Proc. Vol. 476, p213-218, 1998.

Selbrede, et al., Characterization of Parylene-N Thin Films for LowDielectric Constant VLSI Applications, Feb. 10-11, 1997, DUMICConference, 1997 ISMIC—222D/97/0034, 121-124.

Wang, et al., Parylene-N Thermal Stability Increase by oxygenReduction-Low Substrate Temperature Deposition, Preannealing, and PETEOSEncapsulation, Feb. 10-11, 1997, DUMIC Conference, 1997ISMIC-222D/97/0034, 125-128.

Wary, et al., Polymer Developed to be Interlayer Dielectric,Semi-Conductor International, 211-216, June 1996.

Wunderlich et al, Jour. Polymer. Sci. Polymer. Phys. Ed., Vol. 11,(1973), pp 2403-2411; ibid, Vol. 13, (1975), pp1925-1938.

Wunderlich et al., J. Polym. Sci. Polym. Phys. Ed., Vol. 13 1975.

Wunderlich, Macromolecular Physics, Vol. 1-2, 1976.

1. A method of stabilizing a poly(paraxylylene) dielectric thin filmafter forming the dielectric thin film via transport polymerization, themethod comprising: annealing the dielectric thin film under at least oneof a reductive atmosphere and a vacuum at a temperature above a beta-1to beta-2 phase transition temperature of the dielectric film; andcooling the dielectric thin film at a rate of 60° C./min or faster to atemperature below the beta-1 to beta-2 phase transition temperature ofthe dielectric thin film.
 2. The method of claim 1, wherein annealingthe dielectric film includes annealing the dielectric film in a presenceof hydrogen.
 3. The method of claim 2, wherein the dielectric film isannealed in a mixture of 20% or less hydrogen in the presence of aninert gas.
 4. The method of claim 3, wherein the inert gas is argon. 5.The method of claim 1, wherein the dielectric film has a repeat unit of—CF₂C₆H₄CF₂—.
 6. The method of claim 1, wherein the dielectric film isannealed for a time in a range between approximately 1 and 120 minutes.7. The method of claim 6, wherein the dielectric film is annealed for atime in a range between 3 and 5 minutes on hot plate.
 8. The method ofclaim 7, wherein the dielectric film is annealed at a higher temperaturethan a maximum processing temperature used in later integrated circuitprocessing steps.
 9. The method of claim 1, wherein the reductiveatmosphere includes a mixture of a reductive gas and an inert gas, andwherein the reductive gas has a concentration in the mixture of lessthan or equal to 20% by volume in the inert gas.
 10. A method ofstabilizing a poly(paraxylylene). dielectric thin film after forming thedielectric thin film via transport polymerization, the methodcomprising: annealing the dielectric thin film under at least one of areductive atmosphere and a vacuum at a temperature above a reversiblesolid phase transition temperature of the dielectric film to convert thefilm from a lower temperature phase to a higher temperature phase,wherein the solid phase transition temperature is higher than a glasstransition temperature and lower than a melting temperature; and coolingthe dielectric thin film at a sufficient rate to a temperature below thesolid phase transition temperature of the dielectric thin film to trapsubstantial portions of the film in the higher temperature phase. 11.The method of claim 10, wherein the poly(paraxylylene) dielectric thinfilm has a repeat unit of —CF₂C₆H₄CF₂—.
 12. The method of claim 10,wherein annealing the dielectric film under a reductive atmosphereincludes annealing the dielectric film in a presence of hydrogen. 13.The method of claim 12, wherein the dielectric film is annealed in amixture of 20% or less hydrogen in the presence of an inert gas.
 14. Themethod of claim 13, wherein the inert gas is argon.
 15. The method ofclaim 10, wherein the dielectric film is annealed for a time betweenapproximately 1 and 120 minutes.
 16. The method of claim 10, wherein thedielectric film is annealed for a time between approximately 3 and 5minutes on hot plate.
 17. The method of claim 10, wherein the dielectricfilm is annealed at a higher temperature than a maximum processingtemperature used in later integrated circuit processing steps.
 18. Themethod of claim 10, wherein the solid phase transition is a beta-1 tobeta-2 phase transition.
 19. The method of claim 10, wherein the film iscooled at a rate of at least 1° C./second.
 20. The method of claim 10,wherein the film is cooled at a rate of between 1° C./second and 5°C./second.